1. Field of the Invention
The present invention relates to herbicides and, more particularly, to herbicides for the control of preplant burndown.
2. Background of the Invention
Providing a newly planted crop an even start with weeds has been a major objective of modern weed management systems. Whether in conventional tillage or no-till there is a need to plant the crop in a weed-free seed bed. Weeds present at planting will grow much quicker than the crop and, thus, become competitive very early in the growing season. A complete removal of weeds from the soil with herbicides before planting is referred to as a xe2x80x9cburndown.xe2x80x9d
Performing a herbicide burndown one to three weeks before planting a crop, such as corn, allows vegetation to decompose and allows for retreatment if necessary. Using triazines, such as atrazine, for burndown is useful in removing broadleafs but is not adequate for many grasses, such as rye grass. Gramoxone (paraquet) is about 75-80% effective against rye grass and has some effectiveness against broadleafs. The combination of atrazine and paraquat is 85-95% effective against broadleafs and grasses, including rye grass, but is not as effective on vetch. Vetch is a winter annual legume and must also be controlled in burndown. Atrazine is 65-75% effective against vetch and paraquet is also 65-75% effective against vetch. Atrazine plus paraquat is 75-85% effective against vetch. In order to achieve this level of effectiveness on rye grass and vetch, atrazine must be administered at 1.6 to 2.0 lbs. active ingredient per acre and paraquat at 0.5 to 1.0 lbs. active ingredient per acre.
Ametryn gives control of both broadleafs and grasses. Ametryn is also known to be 100% effective against vetch. Nevertheless, Ametryn alone or in mixtures is not recommended for burndown and is not known to be useful in burndown.
Atrazine and paraquet are restricted-use herbicides. Atrazine is restricted because of its potential for ground water and drinking water contamination. Paraquat is restricted because of its high toxicity to humans and other mammals, having an EPA toxicity class I rating. Ametryn, on the other hand, is unrestricted because it has minimal human toxicity and much less potential to contaminate ground water or drinking water, compared to atrazine.
I have discovered that ametryn in combination with reduced amounts of atrazine and paraquet is a superior composition for use in burndown, and is less toxic and less contaminating than the combination of atrazine and paraquet presently in use.
The present invention is a composition of ametryn, atrazine, and paraquat as active ingredients in the proportions of ametryn 1.14 to 1.52 lbs. to atrazine 0.25 to 1.0 lbs. to paraquat 0.25 to 0.5 lbs. The percentage of each herbicide by weight in the composition is, thus, ametryn about 50-60%, atrazine about 20-35%, and paraquat about 17-23%. 1.0 to 3.5 lbs. of this composition is suspended in 20 gallons of water plus 0.5% v/v surfactant or 1 pint of crop oil concentrate, to apply per acre. This composition is applied 5 to 21 days before planting. Field tests show that this composition of the present invention will produce a 92-100% burndown, including rye grass and vetch. Because of significant reduced amounts of atrazine and paraquat in the present composition, there is significantly less human toxic exposure and ground water and drinking water contamination with this composition, compared to the standard use of atrazine combined only with paraquat for burndown. An advantage of the present invention is a preplant burndown herbicide composition which provides less human toxic exposure and less ground water and drinking water contamination.
Another advantage of the present invention is a preplant burndown herbicide composition which produces 92-100% burndown, including rye grass and vetch.
Another advantage of the present invention is a preplant burndown herbicide composition which is relatively inexpensive.
The present invention provides a composition and process for killing weeds and grasses, and, more particularly, for early (rapid) preplant burndown to prepare a field for planting, such as, for example, corn. The herbicidal composition of the present invention may be used directly to kill plants but is preferably used in the form of a liquid or solid formulation suitable for manual or mechanical application to a field. The herbicidal composition of the present invention comprises (i) ametryn [2-(ethylamino)-4-isopropylamino-6-methylthio-s-triazine], (ii) atrazine (2-cloro-4-ethylamine-6-isopropylamino-s-triazine), and (iii) paraquat (1,1-dimethyl-4,4-bipyridinium). This composition also comprises known salts of these active ingredients.
The proportion of ametryn in the composition of the present invention is 30 to 75 percent by weight active ingredient, preferably 50 to 60 percent. The proportion of atrazine is 10 to 40 percent by weight active ingredient, preferably 20 to 35 percent. The proportion of paraquat is 10 to 40 percent by weight active ingredient, preferably 17 to 20 percent. As examples of typical proportions of preferred compositions of the present invention there may be mentioned ametryn: atrazine: paraquat, ratios of about 1:0.4:0.3 and about 1:0.2:0.2. On a weight basis, the composition of the present invention contains, for example, 1.14 to 1.52 lbs. of ametryn, 0.25 to 1.0 lbs. of atrazine, and 0.25 to 0.5 lbs. of paraquat, as active ingredients applied per acre.
Compositions of the present invention include both dilute compositions, which are ready for immediate use, and concentrated compositions, which require to be diluted before use, usually with water. Preferably the compositions contain from 0.6 to 90 percent by weight of the agriculturally acceptable herbicide amandtryn. Dilute compositions ready for use preferably contain from 0.1 to 2% of the agriculturally acceptable herbicide ametryn, while concentrated compositions may contain from 20 to 90% of agriculturally acceptable herbicide ametryn although from 60 to 80% is usually preferred.
The solid compositions may be in the form of granules, or dusting powders wherein the active ingredient is mixed with a finely divided solid diluent, e.g. kaolin, bentonite, kieselguhr, dolomite, calcium carbonate, talc, powdered magnesia, Fuller""s earth or gypsum or a combination thereof. They may also be in the form of dispersible powders or grains, comprising a wetting agent to facilitate the dispersion of the powder or grains in liquid. Solid compositions in the form of a powder may be applied as dusts.
Liquid compositions may comprise a solution, suspension, or dispersion of the active ingredients in water optionally containing a surface-active agent, or may comprise a solution or dispersion of the active ingredient in a water-immiscible organic solvent which is dispersed as droplets in water. The herbicidal composition is suitable either for tank mixing to produce a dilute composition ready for immediate use or for the formation of a concentrate.
Surface-active agents may be of the cationic, anionic, or non-ionic type or mixtures thereof. The cationic agents are, for example, quaternary ammonium compounds (e.g. cetyl-trimethylammonium bromide). Suitable anionic agents are soaps; salts of aliphatic mono ester of sulphuric acid, for example sodium lauryl sulphate; and salts of sulphonated aromatic compounds, for example sodium dodecylbenzene-suphonate, sodium, calcium, and ammonium lignosulphonate, butylnaphthalene sulphonate, and a mixture of the sodium salts of diisopropyl and triisopropylnaphthalene-sulphonic acid.. Suitable non-ionic agents are the condensation products of ethylene oxide with fatty alcohols such as oleyl alcohol and cetyl alcohol, or with alkylphenols such as octyl- or nonyl- phenol or octyl-cresol. Other non-ionic agents are the partial esters derived from long chain fatty acids and hexitol anhydrides, for example sorbitan monolaurate; the condensation products of the partial ester with ethylene oxide; the lecithins; and silicone surface active agents.
The solutions or dispersions may be prepared by dissolving the active ingredients in water or an organic solvent optionally containing wetting or dispersing agent(s) and then, when organic solvents are used, adding the mixture so obtained to water optionally containing wetting or dispersing agent(s). Suitable organic solvents include, for example, ethylene dichloride, isopropyl alcohol, propylene glycol, diacetone alcohol, toluene, kerosene, methylnaphthalene, xylene or trichloroethylene, or a combination thereof.
The compositions for use in the form of solutions or dispersions are generally supplied in the form of a concentrate containing a high proportion of the active ingredients, and the concentrate is then diluted with water before use.
Other additives and adjuvants may also be present in compositions of the present invention. Examples include anti-freeze agents such as ethylene glycol and propylene glycol; dyes; dispersants; rheological agents; anti-foam agents such as silicone based agents; and humectants such as ethylene glycol.
The rate of application of the composition of the present invention may depend on a number of factors, but, as a general guide, an application rate of from 0.1 to 10 lbs. per acre is suitable while from about 1 to 3.5 lbs. per acre may be preferred. Application may be 5 to 40 days before planting a crop, preferably 5 to 21 days.
The compositions of the invention may also comprise one or more additional compounds which possess biological activity.
The compositions of the present invention may be supplied in pre-mixed form or may be tank mixed shortly before application.